Variable capacity compressor



April l 6, 1940. I A, v. SAHAROFF 2,197,158

' 1 VARIABLE CAPACITY cournssSok Filed April 7, 1937 9 Sheets-Sheet 2 I 6.9. SQHAR oFR 16, 1940- A. v.. SAHAROFF' 2,197,158

VARIABLE CAPACITY COMPRESSOR Filed April "7, 1957 Sheets-Sheet 3 fillsel-laaoFF.

INVEN TOR ATTORNEY April 16, 1940. A. v. 's qAg'oF "2,197,158

' gnaw CAPACITY courREssoa 9 Sheets-Sheet 4 v Filed April 7, 195,7

April 15, 1940- A. v. SAHAROFF 7, 58

VARIABLE CAPACITY COMPRESSOR Filed April 7, 1937 9 Sheets-Sheet 5 ///vun U. SaHeRpFF,

IN VENT OR A TTORNEY 9 Sheet -s 6 L SGHQROFF.

INVENTOR TORNEY 9 Sheets-Sheet 7 A. V. SAHAROFF VARIABLE CAPACITY COMPRESSOR Filed April 7. 1957 A ri! 16, 1940.

A W W All/4% G. U. SGHARZOFF.

INVENTOR ATTORNEY April 16, 1 940.

A. v. sAHARoF VARIABLE CAPACITY COMPRESSOR- 9 Sheets-Shet? 8 Filed April 7. 1937 NNN W9 6.0. sefiem IN VENT OR ATTORNEY April 16, 1940- A. v. SAHAROFF VARIABLE CAPAQI TY CQIVIPRES 30R Filed April 7, 1937 9 Sheets-Sheet 9 "G. QSAHAR F.

INVENT OR ATTORNEY Patented Apr. 16, 1940 UNITED STATES PATENT OFFICE VARIABLE CAPACITY OOMPRES 808 Application April '1, 19:7, Serial Nb. 135,468 11 Claims. (cl. 230-217 This invention relates to air or gas'compressors and more particularly to a 'variable volume control mechanism for compressors.

An object of the present invention is to provide a volume control mechanism for a constant speed compressor responsive to pressure at some point in the system as, tor example, the intake of the compressor, operating on one or more clearance pockets in such a manner as to vary the degree of unloading' eifected by theclearance pockets gradually and uniformly and thus involving in efi'ect an infinite number of steps in the loading and unloading process whereby the capacity oi! the compressor will be automatically adjusted to maintain a constant pressure.

More specifically, an object of the present invention is to provide a volume control mechanism for compressors embodying a clearance chamber or chambers and a port or ports establishing communication between the compressor cylinder and the clearance chamber or chambers together with a movable valve controlling and limiting the amount of port opening or closing, thereby controlling and limiting the amount of air or gas,

interchanged between the cylinder and the clearance chamber or clearance chambers which controls and limits the extent to which the final pressure is built in the clearance chamber,

thereby controlling and limiting the amount .0! efiective imloading or loading which the clearance chamber can give to the compressor cylinder which permits use of a large clearance chamher with a large degree of unloading to be used for controlled and limited degree of unloading of the compressor cylinder the same as if the size of the clearance pocket itself was varied fordifierent degrees of unloading. In compressor installations wherein the volume control of the compressor must be arranged to maintain a constant pressure at the discharge or in the intake pipe of the compressor, such as for example oil refinery installations wherein motor driven compressors are employed for pumping gases from stills, the approved type of step by step volume control oi the compressor, loading and unloading it in predetermined fractional proportions of its capacity, is not always satisfactory. Such variable volume control mechanisms are in some instances satisfactory for the reason that if the governing mechanism is, made sensitive enough to control the intake pressure within sufiiciently-narrow limits to meet the requirements, it must necessarily change from one step to the next step in such rapid succession as to bring about an objectionable condition of hunting, especially in those installations where the volume contained in the intake line to the compressor is limited.

An object of the present invention is to provide a variable volume control for overcoming the difliculty above set out, which control provides a clearance pocket or a limited number of clearance pockets for controlling compressor capacity, and a. valve arrangement for establishing and controlling communication between the clearance pocket or the several clearance pockets and the compressor cylinder by gradually and slowly increasing or decreasing the size of the opening or openings between the compressor cylinder and the clearance pocket or pockets, whereby whenany particular clearance pocketis opened throttling occurs in the initial part of the opening action so as to limit the amount of gas taken into and discharged from the clearance pocket. As the valve is gradually opened to a wider and wider position, the throttling is decreased in magnitude in proportion to the degree of opening of the valve and as the'total unloading capacity of the particular clearance pocket becomes gradually more fully available.

Another object of the present invention is to provide means for reducing to a. minimum the economic loss imposed on the cycle of operation of the compressor by the throttling action of. the clearance pocket controlling valve, in instances where such losses are occasioned.

A further object of the present invention is to provide a variable volume control mechanism for air or gas compressors, whereby the valve controlling communication between the clearance pocket or pockets and the compressor is directly connected by mechanical means to a pressure operated mechanism, operation of which in turn is controlled by pressure variances in any suitable pressure area such asthe intake or discharge of the compressor.

With these and other objects in view, as may appear from the accompanying specification, the

, invention consists of various features of construction and combination of parts, which will be first described in connection with the accompanying drawings, showing a variable capacity compressor of the preferred form em ng the invention, and the features forming the invention will be specifically pointed out in the claims.

In the drawings: Figure 1 is a side elevation of a compressor cylinder showing ,the variable volume control mechanism associated therewith.

Figure 2 is a longitudinal sectional view through a part of a compressor cylinder showing one form of the improved variable volume control mechanism associated therewith, however, in this view and subsequent views, the motor which operates the control valve is not shown.

Figure 3 is a cross section taken on the, line 93 of Figure 2 and having parts broken away. Figure 4 is a view similar to Figure 2showing a modified form of the control mechanism in longitudinal section.

Figure 5 is an enlarged detail sectional view of a part of the control mechanism of. the type illustrated in Figure 4.

Figure 6 is a fragmentary cross section taken on the line 6-6 of Figure 4.

Figure '7 is a detail end view of the valve cylinder of the control mechanism.

Figure 8 is a side elevation of a compressor cylinder showing a further modified form of the variable volume control mechanism associated therewith and showing this latter mechanism in longitudinal section;

Figure 9 is an enlarged detail-section of the control mechanism illustrated in Figure 8. The control mechanism illustrated in Figures 8 and 9 embodies a plurality of clearance pockets or chambers for controlling the capacity of the compressor, whereas the forms in Figures 1 to '7 inclusive embody a single clearance pocket or chamber.

Figures 10, 11, 12 'and l3 are detail cross sections taken respectively on the lines lfl-lll, Hl I, l2l2, and l3l3 of Figure 9 and showing the sequencein the unloading of the compressor cylinder with the type of variable volume control mechanism shown in Figures 8 and 9.

Figure 14 is a view partly in side elevation and partly in longitudinal section of a further modified form of the compressor control mechanism. Figure 15 is a cross section on the line 15-45 of Figure 14. u

Figure 16 is a view partly in side elevation and partly in longitudinal section of.a still further modified form of the variable volume control mechanism for the compressorshowing a plurality of clearance pockets for controlling the capacity of the compressor which clearance pockets are arranged in longitudinal end to end relation to each other in contradistinction to the radial re- .lation of the clearance pockets as shown in Figures .9 to 15 inclusive.- Figure 17 is a longitudinal sectional vie through another .modified form of the variable volume control mechanism illustrating such mechanism embodying a'singleclearance pocket and embodying means for reducing to a minimum the. economic loss imposed on eachcycle of operation of the compressor by the throttling action of the clearance pocket controlling valve. Figure 18 is an enlarged fragmentary longitudinal section of the form shown in Figure 17.

Figure 19 Ba cross section' taken on the line I9l9 of Figure18.

compressor in which the clearance pockets are arranged circumferentially-about the compressor cylinder in contradistinction to being located in the head of the compressor as shown in Figures 1 to 20 inclusive and showing clearance kets in the head and crank ends of the co pressor together with the mechanism, diagrammatically shown, for controlling the operation of the unloading valves.

Flgure 22 is a cross section on the line 22-22 of Figure 21, showing communication between the valve cylinder and certain of the clearance pockets.

Figure 23 is a view similar to Figure 22 showing the communication between the valve cylinder and certain other clearance pockets.

Figure 24 is a detail view partly in section of the servo-motor employed in the variable volume control mechanism.

Referring more particularlyto the drawings,

- Figure 1 of the drawings shows a side elevation of a compressor embodying a cylinder l and having a head 2 ,detachably connected thereto in which the clearance pocket or clearance pockets specifically shown in various subsequent figures, are located and in which the control valve which will also be specifically described hereafter is located. The control valve is operated by a shaft 3 which is directly connected in any suitable manner such as by a coupling 4 to the shaft 5 of the servo-motor 6. The servo-motor 6 is of approved type which can be purchased on the ciprocated by pressure fluid from any suitable source, which maybe a source entirely outside or independently of the pressure'system in which the compressor is associated. The delivery of the pressure operating fluid to the cylinder 8 is controlled by the pilot valve 9 while the operation of the pilot valve 9 is in turn pressure controlled either by the suction or discharge pressure of the compressor or' from any approved pressure area such as the pressure within the intake pipe to the compressor, the pressure at the discharge of the compressor or, the pressure in a receiver (not shown) into which the compressor might discharge. The controlling pressure enters the servo-motor through the inlet pipe l0 and acts on the diaphragm II for rocking the lever l2 on its pivot 13 to control operation of the pilot valve 9 and consequently control movement of the piston I of the servo-motor. It is understood that the pilot valve 9 controls the delivery of the piston operating'pressure fluid to the opposite ends of the? cylinder 8 for moving the piston 'I either towards or away from the compressor cylinder I for controlling theloading and unloading of. the compressor ln accordance with variations of the pressure in the pressure area, which is connected to the servo-motor through the pipe III for operating the diaphragm I I.

It is understood that the servo-moto as shown in Figures 1 and 24 of the.,drawlngs is} to the valve operating rod of all oft forms of the variable volume control mechanism shown in Figures 1 to-20 inclusive of the drawings in the same manner as shown in Figure 1 of the drawings.

Referring particularb to the form of variable volume control mechanismvfor compressors illustrated in Figures 2 and 3 of the drawings, the compressor cylinder 20 in which the piston 2| reciprocates has the head 22 attached to the head end thereof in any suitable manner.. The head 22 corresponds to the head 2 in Figure l of the I 9,167,158 drawings and it has a substantially cylindrical 4 thereof and it also extends through the inner end of the head, having its inner end 26 facing the interior of the compressor cylinder 2.0. The inner end 2|/ 0! the head 22 has opening therein through which the inner end of the valve cylinder' 24 extends, and it also has a counter-bore 28 extending inwardly from the compressor cylinder as clearly shown in Figures 2 and 3 of the drawings. The counter-bore 28 forms an annular ring-like opening which communicates with the interior of the compressor cylinder 29 and with the interior of the valve cylinder 24 through the radial inclined openings 29. The valve cylinder 24 is also provided witha plurality of radial openings or slots opening from the interion of the valve cylinder into the clearance pocket or chamber 23 A piston valve 3| is mounted for reciprocatory movement in the valve cylinder 24 and its piston rod 3|, which corresponds to the piston rod 3 in. Figure 1 of the drawings is connected to a servomotor as shown in Figure 1, the general view.

When the pressure entering the pipe ||l oi the servo-motor 6 is'such' as to require reduction in the volume of the capacity of the compressor, the servo-motor will be operated to move the valve 3| outwardly from the position shown in Figure 2 of the drawings. The operation of the servomotor will be such that the valve 3| will be slowly moved outwardly, gradually uncovering the ports 29 and opening them to the interior of the valve cylinder 24, the interior of which cylinder will act 7 ports 29 into the interior of the valve cylinder 24, l

as a clearance pocket. Upon the compressing and discharge movement of the piston 2| a predetermined portion of the fluid compressed in the h d end of the cylinder will pass through the depending upon the degree of opening of the ports 29, this proportion of the capacity of the head end of the compressor increasing as the area of the opened parts of the ports 29 increase.

' When the valve 3| has been moved sufliciently to completely open the ports 29, then the full capacityof the valve cylinder 24 will be operative as a clearance pocket or chamber for reducing the output oi. the compressor an amount proportional to the capacity of the valve cylinder 24. On the suction or intake strokes of the piston 2l'oi' the compressor, the air or gas which has passed into the interior of the valve cylinder 24 will be drawn back into the cylinder 29 of the compressor through the ports 29 and the'annular or ring-like port 28.

As the pressure of the fluid in the controlling pressure area varies further, it will continue to operate the servo-motor 6 for moving the piston valve 3| farther out, and after a predetermined distance of movement of the piston valve 3| and after the. full capacity of the valve cylinder 24 has been utilized as a clearance pocket, the move- .ment of the piston valve 2| will gradually openthe ports 30. The initial opening of. the ports 39 as well as of the ports 29 provides a throttling action which limits the flow of the-air or gas from the cylinder 29 into the clearance pocket formed by the valye cylinder 24 or into the clearance pocket '23. The throttling gradually decreases in magnitude in proportion to the degree of opening of the respective openings or ports, so

that by the gradual movement of the piston valve fractional portion of its capacity, which may be the entire. capacity, represented by the capacities of the clearance pocket or chamber within the valve cylinder 24 and the clearance pocket or chamber 23.

Upon a reverse variation of pressure in the controlling pressure area, the servo-motor 6 will be operated in a reverse direction which will slowly and gradually move'the piston valve 3| inwardly closing the ports 30 and 29 in the same or substantially the same increment in which they are opened. The speed and degree of opening and closing of the ports 29 and 39 respectively depends of course upon the degree of variation of pressure in the controlling pressure area. 7

The controlling pressure area may be the pressure at the inlet of the compressor cylinder 2||,

may be the pressure at the discharge of the compressor or any other suitable pressure area. such as a receiver (not shown) into which the compressor discharges.

The throttling of the openings 29 and 30 and consequently the throttling of the passage of the air or gas from'the compressor cylinder 26 into the clearance pockets or chambers imposes an economic loss on the cycle of operation of the compressor, which economic loss is of course reduced proportionately to the number of steps on increments provided in the unloading of the com-g pressor. However, in order to reduce such economic loss to an absolute minimum, the form of the invention disclosed in Figures 4 to l inclu-- sive is provided.

In this modified form shown in Figures 4 to 'l of the drawings, the head 40 corresponds to the heads 22 and 2 and it has a clearance pocket 4| formed therein'by the walls of the head 40 and the valve cylinder 42. Communication is had with the interior of the compressor cylinder through an annular or ring-like port 43 which corresponds to the annular or ring-like port 28, radial ports 44 in the cylinder 42, and from the valve cylinder 42 through the plurality of radial ports 4.5 to the clearance pocket 4|.

The valve 41 has a valve rod 48 connected thereto which is connected in turn to a servomotor such as the servo-motor 9 and the valve 41 is'operated inexactly the same manner as the valve 3|, such operation having been heretofore disclosed.

The clearance chamber 4| is shown in the drawings as eccentric of the valve cylinder 42, but theinvention is. not to be so limited. The clearance pocket 4| has an outlet port 49 communicating therewith and communicating with the interior ofthe compressor cylinder 59. This outlet port 29 is controlled by an automatic check valve 5| oi any'approved type but preferably of the "Feather valve type such as disclosed in Letters Patent Number 1,916,685. This automatic check valve 5| is so positioned and operates in such manner as to allow ful-egress from the clearance pocket 4| into the compressor cylinder 50, but at the same time enbodies partial ingress to the cylinder in proportion to the amount of the opening of the ports by the valve 41. In otherwords the throttling of the air 'or gas as it passes from the compressor cylinder 50 to the clearance.

sufliciently large, there will be practically no throttling of the air or gas when it passes from the clearance chamber to the cylinder and thus the economic loss which would be occasioned by the throttling of the opening or port 45 by the valve 41 will be eliminated.

The valve cylinder 42 is preferably formed of a cylinder normally open at both ends with its inner end closed by a closure plate 63. The closure plate 56 may be attached to the cylinder 42in any manner such as by the bolts or tap screws 64. An end view of the valve cylinder is shown in Figure 7 of the drawings.

The present invention comprehends the provision of any predetermined number of clearance chambers or pockets for unloading the compressor which are successively brought into and out of unloading communication with the compressor cylinder, and in Figures 8 to 13 inclusive of the drawings is illustrated a further modification of the variable volume control for a compressor which embodies a plurality of clearance pockets or chambers. v

In this form of the variable volume control mechanism, the clearance head 66, which corresponds to the clearance heads 2 and 46, has an annular space therein provided by the walls'of the clearance head and the valve cylinder 62. :This annular space 63, however, is divided into a plurality of radially disposed clearance chambers or pockets 64, 65, 66 and 61 by the partitions 66 as clearly shown in the cross sectional views III to B inclusive,

The inner end 66 of the head 60 is provided with a central bore through which the end 01' the valve cylinder 62 extends, and it is also pro vided with a counterbore III which provides an annular or ring-like port opening into the compressor cylinder II around the inner closed end I2 of the valve cylinder 62. The valve cylinder 62 is provided with a plurality of radial ports l6 corresponding to the radial ports 26 by means 01' which commlmication is established between the interior of the valve cylinder 62 and the interior of the compressor cylinder II. V

A piston valve I4 reciprocates in the valve cylinder 62 and its rod I5 is connected to a servomotor such as the servo-motor 6 for moving the valve upon pressure variances in the control pres-' sure area. i

In this form of the invention five clearance pockets or chambers are provided which together with their various ports of communication in combination with the slow gradual movementof the'piston valve I4 will provide substantially an infinite number of steps for the unloading and loading of the compressor and consequently provide high sensitive volume control of the compressor cylinder without any hunting or indecisive action on the part of the volume control mechanism.

.Upon initial or small pressure variances in the control pressure area from the predetermined desired pressure, the servo-motor will act to move the piston valve I4 outwardly and gradually arcane continued in its outward movement by operation of the servo-motor and as it moves outwardly it gradually opens the port II which opens the clearance pocket 64 to the compressor cylinder 'II which increases the clearance capacity and consequently decreases the discharge volume of the compressor in proportion to the capacity of the clearance pocket I6 and the clearance pocket 64. The active clearance area of the clearance pocket or chamber 64 is of course gradually varled in increments of its capacity in proportion to the degree of opening of the port 'I'I until such time as the port 11 is completely open and the full clearance capacity oi the chamber or pocket 64 is utilized. Further outward movement of the valve I4 under further increase in pressure difference from the predetermined desired pressure in the control area. will gradually open the port or passage I6 which opens communication between the clearance pocket 65 through the valve cylinder 62 with the compressor cylinder II. The clearance area of the clearance pocket or chamber 55 is gradually brought into effective operation in proportion to the degree of opening of the port I6 is as the pressure diflerence from the predetermined desired pressure in the pressure area further increases, the piston valve I4 continues slowly in its outward movement and gradually opens or uncovers the port 16 which opens the clearance pocket era-chamber 66 to the compressor cylinder II in gradually increasing increments of its capacity in proportion to the degree of opening of the port I9. Further continued outward movement of the piston valve 14 gradually opens the port 86 which in turn opens the clearance pocket 61 to the compressor cylinder II. When the port 86 is entirely open then all of the clearance pockets I6, 64, 66, 66 and 61 will be open to the compressor cylinder II and active to unload the compressor to zero capacity.

When the pressure diflerence in the control pressure area decreases the servo-motor will act to move the piston valve I4 inwardly and gradually cut oil the various clearance pockets or chambers from communication with the compressor cylinder in a reverse order from that in v which they are opened to the compressor cylinder. It will therefore be seen that with a plurality of clearance pockets or chambers communication of which with the compressor cylinder is gradually controlled, each in a large number of increments of its capacity, that an indefinite number of steps will be provided in the unloading and loading of the compressor cylinder providing practically perfect sensitive volume control of the compressor without any indecisive .or hunting action on the part of the control mecha'nism.

In Figures 14 and 15 is illustrated a modification of the form of variable volume control shown in Figures 9 to 13 inclusive. This form is identical in construction and'operation with the form just described and disclosed in Figures 9 to 13 inclusive except that the clearance pockets 64', 66' and 61' all have ports or passages 64 communicating therewith and communicating with The-ports 64 are the compressor cylinder Il'. controlled-by check valves 66 of any approved type but preferably of the Feather"v valve type such as the valve 5i heretofore described in connection with Figures 4, 5 and 6 of the drawings.

The automatic check valves 65 operate in the same manner as the automatic check valves 5|, that is, they are provided to reduce any economic loss on the cycle of operation 01 the compressor 15 of the head I29. The valve cylinder I22 is proto an absolute minimum and they are so positioned; and the ports 84 are of such size as to allow full egress from the respective clearance pockets to the compressor cylinder I I but at the same time they impose partial ingress to the cylinder in proportion to the amount of valve opening. In other words these valves 85 and the ports v 94 will permit iull discharge of the air or gas from the respective clearance pockets into the compressor cylinder 'II' upon the suction operation of the' compressorand will eliminate the economic loss in the return of the gas to the compressor cylinder which would otherwise be occasioned by the throttling of the various openings I3, 11', "I9", 19' and 89' by the piston valve 14' during the operationof the apparatus.

In Figure 16 a form of variable volume control for a compressor is shown in which a plurality of clearance pockets 99, 9I and 92 are provided in the clearance head 93 and they cooperate with the clearance pocket or chamber formed within the valve cylinder 95 for controlling the degree of unloading of the .compressor cylinder 95. These pockets, however, are each an annular or ring-like pocket and are spaced end to end in the head 93 being formed by suitable ring-like partitions 91 whereas the various pockets 84, 65,

66 and 61 are radial pockets. A piston valve 98 reciprocates in the valv cylinder 95 and it is operated from a servo-motor such as the servo-motorB through the medium of the piston rod 99 in the same manner in which the piston valves of the various forms heretofore described operate. Communication between the compressor cylinder 96 and the interior of the valve cylinder 95 is had through an annular port I99 formed by a counterbore in the innerend IIII of the head 93 and the plurality of radial ports I92Qwhich increase with theradial ports in the various other valve cylinders heretofore described. The various clearance pockets 99, 9| and 92 are opened to the compressor cylinder 95 through the valve cylinder 95 each through a plurality of radially disposed openings I 93, I94 and I95 respectively. These series of radial openings are arranged in longitudinally spaced relation in the valve cylinder 95 so that the clearance pockets are successively opened to the compressor' cylinder 96 as the. valve 99 moves outwardly and are successively cut oil in an inverse succession as the piston valve 98 is moved k inwardly.

' pressor cylinder I22 through the us' 1 In Figure 16 of the drawings the clearance pocket-92 is shown as of greater capacity than the clearance pockets 99 and. 9| and it may be understood that any one of these clearance pockets may be made with a'larger ,area than the other or that all of them may be of the same size without departing from the spirit of the present invention. 'Also while in the various forms heretofore disclosed, such as those including a plurality of clearance pockets, said'pockets have beenshown as or the same size, it is to be understood that such clearance pockets may be of unequal size and/or capacity without departing from the-spirit oi the present invention.

In Figures 17 to 19 inclusive of the" drawings the clearance head I29 is provided with a single substantially cylindrical clearance pocket I2I defined 'by the wallsoi the head I29 and the valve -cylinder I22. The interior of the valve cylinder has communication wlththe interior of the comnular or ring-like port I24 formed in the inner end I25 vided with a plurality of radial poi-ts I29 which, are the same as the various other radial-ports 29, I3, etc. The valve cylinder I22 is provided with a plurality of slots or long ports I2l which establish communication between the clearance chamber or pocket I2I and the compressor cylinder I23 and such communication is controlledby the piston valve I28. The piston valve I28 is operated from a servo-motor such as the servomotor 5 through the medium of the valve rod I29. The valvepiston I28, however, diifers from the valve pistons in the various types heretofore described in that-its inner end is formed of an automatic check valve I39. This check valve I39 may be of any approved type but preferably of the Feather" valvetype as above referred to. The head I3I of the piston valve I29 forms the valve seat which is ported in the usual manner as shown at I32 The ports I32 are controlled by the flexible valve strips I93 and are confined and limited in their movement by the guard I34 which is attached to the head I3I in any suitable manner. The automatic check valve structure I39 is arranged so that it will be closed on pressure fiuid passing inwardly through the ports I26 into the cylinder and prevent any passage of fluid under pressure from the compressor cylinder I23 into the clearance chamber or pocket I2I- except at such times as the piston valve I28 is moved rearwardly under the action of the servo-motor to partially open the ports I21. However, upon the suction operation of the compressor the flexible valve strips I33 unseat and permit free fiow of the fluid under pressure from the clearance pocket back into the compressor cylinder I23. The valve structure I39 is provided to decrease to a minimum economic loss in the cycle oi operation of the compressor which would be occasioned by the throttling action of the piston valve I29 and the openings I21 when the latter openings are only partially opened. The degree or proportion of unloading of the compressor cylinder I23 is controlled by the degree of or the amount that the op I2? are opened forwardly of the piston valve I28 and the openings I21 are entirely opened. At all other times the unloading action of the clearance chamber or pocket I2I is in direct proportion to the degree, of the opening of the ports I2? to the cylinder I23. Thus by the gradual movement of the piston valve I29 outwardly the compressor cylinder I23 may beunloaded in an indefinite number of steps or incrementsbetween the. complete loaded condition and the active incorporation of the entire unloading capacity or area of the clearance chamber or pocket I2I. The compressor cylinder I23 is loaded in an inverse manner by the inward movement of the piston valve I29. I p

In Figure 20 a cross section through a clearance' head I49 is shown which clearance headis divided into a plurality of radial clearance pockets I4I, I42, I49 and I44. These clearance pockets have communicat on with the interior of the valve cylinder I thr ugh openings I45 which correspond tothe various openings", I9, I9 and 99 in Figure 9 oi'the drawings.

In this modified form shown in Figure 20, however, the piston valve I4I has an automatic check valve I49 in its inner .end exactly in the same manner as .the automatic check valve I39, is associated with the piston valve I29. The automatic check valve. I48 operates in exactly the same manner and,i'or the same purpose as the automatic check valve I38.

In all of the various forms heretofore described the various clearance pockets have been illustrated and described as being formed in a clearance head at the 'end of the compressor'and all controlled by a single piston valve. However, in Figures 21 to 23 inclusive a modification of the invention is shown wherein the clearance pockets are formed in the shell of the compressor cylinder and a series of pockets are provided for the head end of the cylinder and a second series of clearance pockets are provided for the crank end of the cylinder. The twoseries of clearance pockets are each controlled by independent piston valves.

Referring more specifically to the modification of the invention shown in Figures 21 to 23 inelusive, the compressor I58 embodies the compressor cylinder I5I 'in which the piston I52 reciprocates. The piston I52 compresses both at the head end I53 and the crank end I54 of the cylinder I 5I. The shell I55 of the compressor cylinder has a set of clearance pockets I56, I51, I58, and I59 formed therein about the head end of the cylinder and a second set of clearance pockets similar in shape and size, as well as in arrangement, about the crank and of the compressor cylinder. pockets I56 to I59 inclusive are controlled by a control valve structure I6I while the clearance pockets I68 about the crank end of the cylinder are controlled by a control valve structure I62.

The valve structure I6I is similar to and substantially the same as the various control valve structures heretofore described in connection with the various forms of the invention illustrated in Figures 1 to 20 inclusive. That is, it

comprises a valve cylinder I63 in which a piston valve I64 reciprocates. The valve cylinder I63 has its inner end I65 closed and it is further provided with a plurality of radial openings or ports I66 which establish communication between the interior of the valve cylinder I63 and the interior of the head end I53 of the compressor cylinder I5I through the medium of anannular ring-like port I61.

The cylinder I63 is provided with a plurality of longitudinally spaced ports I68, I69, I18 and "I. The port I68 opens into the clearance pocket I56. The port I69 opens into a passageway I12 which in turn opens into the clearance pocket I58 while the port I18 opens into a passageway I13 which in turn opens into the clearance pocket I51. The port "I opens into a passageway I14 which in turn opens into the clearance chamber I59. Thus by provision of the various ports I68, I69, I18 and "I together with the passages I12, I13 and I14 the various clearance pockets may be opened to communication with the head'end I63 '01 the compressor cylinder ISI for unloading the head end 01' the compressor cylinder in various proportions of its capacity, such unloading being controlled by the movement of the piston valve I64. While in the drawings, a particular construction or arrangement of passages I12, I13 and I 14 is illustrated, it is to be understood that these passages may be formed or arranged in any suitable manner without departingirom the spirit of the invention, so long as the various clearance pockets may be successively brought into communication with the crank end of the compressor cylinder as the piston valve I64 moves outwardly.

The opening of the clearance I The piston valve- I64 has a piston rod I 15 connected thereto which is in turn connected by an articulate connection I16 to a bellcrank I11. The bellcrank I11 is connected to the piston rod I18 of the servo-motor I19 so that the piston valve I64 will be operated by the servo-motor I19. The servo-motor I19 is similar in its general construction to the servo-motor 6, that is it includes a cylinder I88 in which a piston I8I reciprocates. The reciprocation of the piston I8I operates the piston rodv I18 and its speed of reciprocation as well as its direction of movement is controlled by a pilot valve I82. The servomotor I19 as well as the pilot valve I12 may be purchased upon the open market. The pressure fluid for operating or moving the piston I8I enters the pilot valve from any suitable supply source which may be and usually is a source of.

pressure fluid independently of the pressure fluid circuit in which the compressor I58 is connected, through the inlet pipe I83. That is, in other words, the pressure fluid which operates the piston valve I64 is derived from a. pressure source (not shown) outside of and independently of the pressure fluid circuit of the compressor. The pressure fluid for operating the piston I8I exhausts through the outlet pipe I84. The inlet of the pressure fluid into the cylinder I88 is controlled by the pilot valve I82 for moving the piston in either direction,suitable' ports I85 and I86 being provided, which deliver the pressure fluid to the left hand end of the cylinder I88 and to the right hand end of the cylinder respectively- The pilotvalve is operated or its operation is controlled, rather, from a suitable pressure area in the pressure fluid'circuit of the compressor,

as for instance from the intake pipe (not shown) of the compressor I58 or as desired from the discharge pipe (not shown) of the compressor through a pressure control mechanism I81 commercially known as a "masoneilan control mechanism manufactured and sold by the Mason Neilan Company, and through a .masoneilan" ulator I88 through the inlet pipe I98. The pressure control mechanism I81 operation of which is controlled by the pressure fluid entering the pipe I89, delivers an operating pressure fluid through the pipe I9I to the diaphragm regulator I88. The pressure fluid delivered to the diaphragm regulator I88.operates this mechanism and operates the pilot valve I82 through the leverage connection I92. Thus the piston valve I64 is moved in and out for loading or'unloading the head end 01' the compressor I53 in an infinite number of steps and an inflnite number of increments of its capacity in accordance with the variations in pressure in the controlling pressure area (not shown) which is connected to the pipe I89.

The piston valve I64 moves outwardly, slowly and gradually in the same manner as the piston valves 3|, 41, 14, etc., heretofore-described and 1 action of these ports and consequently provides the utilization of the fractional czipacity of the various clearance pockets compri ng flrst the space or clearance chamber I94 within the valve 15 cylinder I63 and the clearance pockets or chambers I58, I51, I" and IE9. Thus the compressor may be unloaded and loaded in an infinite number oi steps ranging from zero capacity to full capacity by the opening hi the various valve ports in increasing increments controlled by the operation oi the servo-motor I18. 1

The valve i structure I62, while shown only in side elevation is identical in construction with the valve structure I6I and it is connected by means of the'valvebr piston rod I95 to the bellcrank I86 through a suitable articulated connectionlfl. The bellcrank I96 is in turn connected to the piston rod I18 for operating the valve structure I62 by the servo-motor in the same manner in which the valve structure IGI is operated.

The bellcranks I98 may be arranged to oper-. ate the valve structures l6l and I62 in unison or by slight variances in the angles of the bellcranks, the valve structures IGI and I62 may be operated slightly out of synchronism, that is, they may .be operated so that the corresponding clearance pockets in the head and crank ends of the cylinder instead of being opened simultaneously to the respective ends of the compressor cylinder II will be opened in succession.

From the foregoing description taken in connection with the drawings it will be apparent that a variable volume control mechanism for compressors has been provided by means of which a compressor may be unloaded and loaded in an infinite number of steps from '100 per cent capacity to zero capacity by means of the opening of the control valves slowly in-increasing increments, permitting the utilization of fractional portions, the capacities of the predetermined number of clearance pockets in proportion to the degree of opening of the communicating ports between the clearance pockets and the compressor cylinder. Also that a variable volume control mechanism for compressor has been provided in which the control valves are mechanically moved in lieu of being pressure moved as has heretofore been the normal practice and further that the operation of the variable volume control mechanism may be controlled from any suitable pressure area such as the intake or discharge of the compressor cylinder, a receiver into which the compressor discharges, or any other suitable source, the pressure from this 'control area acting to control the delivery of an operating pressure iiuid which may be taken from a source outside of the pressure circuit of the compressor.

.It is to be understood that the invention is ,not to be limited to the specific construction or arrangement of parts shown but that they may be' widely modified within the invention deflned by the claims.

What is claimed is:

1. In a compressor, a cylinder, a' clearance chamber, a valve for controlling communication between said cylinder and clearance chamber, meansffor operating said valve and controlling the extent of opening and closing oi the valve whereby a variable amount of throttling of the communication between said cylinder and clearance pocket is provided for controlling the degree of unloading oi'the cylinder, and an automatic check valve in the line of communication be tween the cylinder and clearance chamber and controlling return of fluid from said clearance chamber to said compressor cylinder, said check valve having sumclent area to permit cylinder.

substantially unthrottled flow of gas from the clearance chamber to the cylinder.

2. In a compressor, a cylinder, a clearance chamber, a valve for controlling communication between said cylinder and clearance chamber,

means for operating said valve and controlling the extent of opening and closing of the valve whereby a variable amount of throttling of the communication between said cylinder and clearance pocket is provided for controlling the degree of unloading of the cylinder, means responsive to pressure variances in a predetermined area for operating said valve operating means, and an automatic check valve in the line of cominunication between the cylinder and clearance chamber' and controlling return of fluid from said clearance chamber to said compressor cylinder, said check valve having suiflcient opening area to permit substantiallyunthrottled flow of gas irom the clearance chamber to the cylinder.

3. In a compressor, a cylinder, a clearance chamber, a valve for controlling communication between said cylinder and clearance chamber, means for operating said valve and controlling the extent of opening and closing of the valve wherebya variable amount of throttling of the communication between said cylinder and clearance pocket is provided for controlling the degree of unloading of the cylinder, means responsive to pressure variances in the suction line of the compressor for operating said valve opening means, and an automatic check valve in the line of communication between the cylinder and clearance chamber and controlling return of fluid from said clearance chamber to said compressor cylinder, said check valve having sufficient opening area to permit substantially unthrottled flow of. gas from the clearance chamber to the cylinder.

a. In a compressor including a cylinder, a variable volume control mechanism including a clearance pocket and a passage establishing communication between the clearance pocket and cylinder, a valve for controlling communication between said clearance pocket and said compressor cylinder, servo-motor for moving said valve, mechanical means connecting said servomotor and valve, 'means responsive to pressure variances in the suction line of thelcompressor for controlling operation oi said servo-motor, and an automatic check valve in said passage and controlling return of fluidfrom said clearance pocket to said compressor said check. valve having suflicient opening area to permit substantially unthrottled return flow of gas from the clearance pocket to the cylinder.

5. In a compressor, a compressor cylinder, a clearance chamber, a valve cylinder between said compressor cylinder and said clearance pocket, said valve cylinder having ports opening into said compressor cylinder and ports opening into said clearance pocket, and a piston valve in said valve cylinder which -.upon opening movement first opens the valve cylinder to the compressor cylinder and subsequently opens the valve cylinder to said clearance pocket and closes the valve cylinder to the compressor cylinder when in closed position said valve piston having an opening thereinwhereby the cylinder behind the valve piston is opened to the compressor cylinder upon opening of the valve cylinder to the compressor 6. Ida compressor, a compressor cylinder, a clearance chamber, a valve cylinder between said compressor cylinder and and clearance pocket,

said valve cylinder having ports opening into said compressor cylinder and ports opening into saidclearance pocket, and a piston valve in said valve cylinder which upon opening movement first opens thevalve cylinderto the compressor cylinder and subsequently opens the valve cylinder to'said clearance pocket and closes the valve cylinder to the compressor cylinder when in closed position, and means for moving said valve gradually in an infinite number of steps for controlling and limiting the amount of port opening and closing thereby providing for unloading and loading the compressor'in an infinite number oi steps between full andzero capacity of the compressor cylinder and said clearance pocket,

said valve cylinder having ports opening into said compressor cylinder and ports opening into said clearance pocket, and a piston valve in said valve cylinder which upon opening. movement first opensthe valve cylinder to the compressor cylinder and subsequently opens the valve cylinder to said clearance pocket and .closes the valve cylinder; to the compressor cylinder when in closed position, and means for moving said valve gradually in an infinite number of steps for controlling and limiting the amount of port opening and closing thereby providing for unloading and loadingthe compressor in an infinite number of steps between-full and zero capacity of the compressor, said valve piston having an opening extending longitudinally therethrough to permit returning of gas from the clearance pocket to the compressor cylinder and a check valve carried by said piston and positioned to prevent flow of gas through the valve piston during port opening movement thereof, said check valve hav ing sufiicient opening area to permit substantially unthrottled return flow of gas from the clearance pocket to the compressor cylinder.

, 8. In a compressor, a compressor cylinder, a clearance chamber, a valve cylinder between said compressor cylinder and said clearance pocket, said valve cylinder having ports opening into said compressor cylinder and ports opening into said clearance pocket, and a piston valve in said valve cylinder which upon opening movement first opens the valve cylinder to the compressor cylinder and subsequently opens the valve cylinder to said clearance pocket and closes the valve cylinder to the. compressor cylinder when in closed position, a return passage between said clearance pocket and said compressor cylinder, and a check valve in said return passage.

9. In a compressor, a compressor cylinder, 9.

clearance chamber, a valve cylinder between said compressor cylinder and said clearance pocket,

said valve cylinder having ports opening into said compressor cylinder and ports opening into said clearance pocket, and a piston valve in said valve cylinder which upon opening movement first opens the valve cylinder to the compressor cylinder and subsequentlyppens the valve cylinder to,said clearance pocket and closes the valve cylinder to the compressor cylinder when in closed position, said piston valve being hollow to permit the interior of the piston valve together with the interior of the valvecylinder to act as an initial clearance pocket upon opening movement of the piston valve; a return passage between said clearance pocket and said compressor cylinder, and a check valve in said return passage.

10. In a compressor, a compressor cylinder, ;a

valve cylinder, a plurality of clearance pockets about said valve cylinder, said valve cylinder provided with a plurality of ports arranged successively along its length and opening one into each of said clearance pockets, said valve cylinder having its inner end closed and provided with ports'in its sides opening into said compressor cylinder, a piston valve in said valve cylinder,

and check valves in said passages, said check valves having sumcient opening area to permit substantially unthrottled return of gasfrom the clearance pockets to the compressor cylinder.

11. In a compressor, a compressor cylinder, a.

piston therein dividing the cylinder into active head and crank ends, a plurality of clearance pockets for the head end of the compressor cylinder, a plurality of clearance pockets for the crank end of the compressor cylinder, a pair of valve cylinders each having a. plurality of successively arranged ports opening into the successive clearance pockets for the head and crank ends of the compressor cylinder respectively, one of said valve cylinders having ports opening into the head end of the compressor cylinder, the other of said valve cylinders having ports opening into the crank end of the compressor cylinder, valve pistons in said valve cylinders controlling said ports, a servo-motor and means connecting said servo-motor to said valve pistons for operating the valve pistons in unison for simultaneouslyunloading the head and crank ends of the compressor cylinder in successive stages of "their capacities.

ALEXANDER. V. SAHAROFF. 

